This invention relates to a four-wheel drive arrangement for motor vehicles, particularly for passenger cars which have an in-line internal-combustion engine mounted, preferably, in front of the front axle and transversely to the longitudinal axis of the vehicle, wherein the internal-combustion engine drives the front and rear wheels via a transmission (e.g., a gear box and a clutch), a differential gear and an angular drive gear assembly.
In a vehicle with four-wheel drive described in German Unexamined Printed Patent Application No. 33 17 247, an angular gear has a relatively long bearing neck, extending in the longitudinal direction of the vehicle, for an output shaft which is connected to a two-part cardan shaft. The length of the output shaft is therefore also relatively long. In addition, the angular gear assembly extends a certain distance from the transversely located internal-combustion engine; i.e., it is fastened only at the differential gear. A disadvantage of this construction is that, due to the angular gear assembly being connected at the output side and to the total length of the bearing neck and its output shaft, whip-like accelerations occur during the operation of the motor vehicle, causing excessive noise on the inside of the vehicle. This noise is further affected by the bending vibrations of the two-part cardan shaft which, via the angular gear assembly, is incited by the second order of the speed of the four-cylinder internal-combustion engine.
An object of this invention is to take such measures at the angular gear assembly, or at adjacent units, and at the cardan shaft of a vehicle equipped with a four-wheel drive so that the inside noise throughout the speed range of the internal-combustion engine does not exceed an acceptable level.
This and other objects are attained, in a four-wheel drive arrangement which comprises a transmission/differential combination for driving a first axle and an angular drive arrangement for driving a second axle, by a number of measures which include providing additional support for the angular drive at a point other than where the angular drive is connected to the transmission/differential unit. This support is preferably provided by a bracket-type support member fastened to an end of the angular drive gear housing and to the internal-combustion engine. The base of the bracket preferably extends vertically over a substantial portion of a housing (e.g., the engine block) of the engine and is located in an area provided with an internal (to the engine housing) transverse support member. The bracket is preferably formed in a stamping, casting or similar process. In another embodiment, the additional support is provided by support flanges formed on the housing of the angular drive and fastened directly to the engine housing.
In an especially advantageous embodiment of the present invention, the transmission includes a gear box and a clutch assembly, and the housing of the clutch assembly and the differential gear is formed as an integral housing unit. The integral housing preferably includes a support flange or neck for a bearing which is reinforced by a plurality of radially extending ribs on the housing. A number of lugs are provided around an outer wall of the housing for use in fastening the housing to the angular drive. At least some of the ribs preferably extend in the direction of the lugs. In an especially preferred embodiment, the outer wall of the housing is substantially uniform in height around at least a portion of the housing, especially along a transitional portion of the housing between the clutch and differential gear. The housing also preferably includes a supporting web, extending circumferentially around at least a portion of the housing, inside of the outer wall.
In an especially preferred embodiment of the invention, the angular drive includes an angular drive gear arrangement and a cardan shaft arrangement connected to an output shaft of the angular drive gear by a resonance decoupling device. The cardan shaft arrangement preferably comprises three sections. The center section is preferably connected to the end sections by synchronous joints and the output end of the arrangement is preferably connected to a differential gear associated with the second axle by a resonance decoupling device. The resonance decoupling device preferably includes an elastic (e.g., rubber) disk. The center section of the shaft is also preferably supported by bearings mounted on an adjacent wall surface (e.g., the floor board) of the vehicle.
In yet another especially preferred and advantageous embodiment of the invention, the angular drive gear assembly includes an output shaft supported by a bearing which is situated in a neck or flange which extends, along a longitudinal axis of the vehicle, for a relatively short distance from the angular gear assembly. A connecting element is provided on the output shaft for connecting to the cardan shaft arrangement. The connecting element preferably extends only slightly beyond the open end of the bearing neck.
The main advantage achieved by means of the present invention is that, by supporting the angular gear assembly at the internal-combustion engine, and due to the relatively short overall length of the bearing neck and of the output shaft, and through use of resonance decoupling of the output shaft from the angular gear assembly, noise levels inside the vehicle during operation are low. The bracket-type support is not only easy to manufacture, but can also be fastened without problems at the angular gear assembly and at the internal-combustion engine, for example, by means of screws. When the effective base of the support extends over a significant part of the height of the internal-combustion engine housing, relative movements between the angular gear assembly and the internal-combustion engine are largely avoided. The connection of the support at a partition or transverse support of the internal-combustion engine ensures effective operation.
The advantages gained with respect to lower inside noises are enhanced also by the fact that the clutch housing and the differential gear housing are combined into one constructional unit, and that the bearing neck of the differential gear, with respect to its outside wall, is supported by star-shaped ribs. Also contributing to this behavior are the outside walls of the housing which extend around the bearing neck without any significant contractions, as well as the supporting web which extends between the outside wall and the bearing neck of the differential gear housing.
Finally, the three part cardan shaft arrangement of the present invention operates without resonance while in connection with an upright and transversely installed four-cylinder in-line internal-combustion engine running up to a speed of 7,000 revolutions per minute. In this regard, the synchromesh joints also ensure a uniform rotating motion of the center shaft section when the shaft sections, for constructional reasons, are not located in one plane.
Further objects, features and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings, which show for purpose of illustration only, an embodiment constructed in accordance with the present invention.